LPG Discussion Forum

When I was really young I built a fair few single point gas/petrol generators, they were just small petrol engine (honda gx) single cylinder with a crude mixer ring inbetween the carb/air filter with a small reducer . They used to start on petrol then you would switch to gas when warm. I always used to think they were set up badly by our test dept.
Twelve years later I think I might be working on refurbing some . These ones now seem to run calor gas bottles only, not even started on petrol and they go alright from cold the ones that I saw working, I did'nt get a good look though. They seem to be the same small engine , crude ring mixer and small reducer jobbie. I can get them running ok but would obviously trust the knowlege on here better for a proper way to set them up if anyone could hazzard a quess.

I do a lot of work on the Honda GX160 and 270 engines on LPG.

The best setup I have found so far is using the honda LPG carb and lovato reducer. All you need to adjust is the tick over setting on the reducer. They can be lumpy and not keen idle when cold but once warm all is ok.

You can convert the petrol carb rather than but the proper carb but it is a bit of faffing.

Thanks, handy to know. I did'nt know there was a lpg carb. Might be worth upgrading these sets.

The LPG carb is jetted perfectly, is slightly differntly flowed and the choke flap is smaller so it does not fully block off teh air flow. You need to use the choke to start.

Interesting, the ones I saw yesterday started from cold on lpg on the key with no visible use of the choke, did'nt get to see how that worked. Some of them had been standing for years but started straight away from a calor bottle on the key. Must get a closer look, there was a wire going to the reducer.
These were hospitality units, office, toilet and genny.

Where can I purchase the Honda Keihin lpg carbs for the GX390 Classicswede, or can you supply them?

I can find out price for you. How many would you be wanting? Qty would effect price

Most mixer systems will start from cold on gas with no problem. No choke required (it would just f*** up the mixture), just a little initial priming - though with next to no intake tract to gas up, I suspect not even that.
I'd have expected setup to be much the same as for any open loop mixer system - except that you don't have an idle, only different powers at one engine speed.

I've not checked pricing on these yet I'll try and do it asap.

Starting on gas with electric start is no problem but pull starting you want them to start as fast as possible and using some choke helps these little engines helps them suck enough on the vapouriser at low cranking speed.

Yes, the Honda GX 390 models we have use the small engine Lovato reducer which Tinley have on their site. The 12v solenoid on the front of the vapouriser is operated during cranking by a timer set to operate for 10 seconds. This solenoid presses the diaphram and starts the thing the same as pressing the small button in the middle of the vapouriser on non-electric start models. There is a normal 12v solenoid fitted for cutting off gas flow too. It's a bit overkill having a timer as wiring the vap choke to the starter motor solenoid would do the same thing. Trouble is, typical generator designers like to fit electronics on carb generators and old diesel engines even down to a circuit to cut the engine if the alternator/ battery charger fails which is annoying as I get called out to plenty both petrol and diesel that start then stop after a few seconds and it turns out to be a charging problem and the electronics fitted to the start module are shutting the engine down. Hate that mod, I would programme it out on every generator if I could.
The larger v-twin, 600+ cc petrol carb generators we have (honda and Briggs) use a large Lovato reducer the type you see on older cars. The water lines are not used on the reducer as we are air cooled obviously , they are just mounted somewhere warm in the generator cabinet away from the cold air in duct. They have a AEB electronic box fitted too which has 2 switches on top, cant make out which model as they are faded. There is no choke type solenoid fitted on these just a normal one as on our cars to cut off gas flow. They still start from cold though on gas and run full load instantly when fitted to hospitality unit heaters as this is what customers demand.
Interestingly when I started servicing these generators recently they had never had the 12v solenoid (valtec) filters changed as nobody before me knew they had them fitted untill I pointed out my boss said. They are all around seven or eight years old and also have a small wire mesh filter fitted in the gas pipe at the gas bottle connections similar to the ones in your washing machine water hoses. Every filter I have removed has been spotless, not even staining on the paper and they have had lots of use.

billynoband wrote:Every filter I have removed has been spotless, not even staining on the paper and they have had lots of use.

I'm guessing these are run from bottles, and using the bottles "right way up" so drawing off vapour rather than liquid ? I;d guess that'll work for the sort of sizes you are talking of, but sometimes the bottles will get a bit frosty The reducer is acting as just a pressure reducer - and won't have the heat requirements of evaporating the liquid.
If that is the case, then I'd expect the filters to stay very clean - most of the sort of things they filters are there to collect will stay in the bottle. Of course, when someone like myself comes along and upends the bottle, I get all that crud and heavy ends that others left behind - or used to, I don't use bottles any more as we've got two reasonably prices outlets locally. The Disco (which was mostly filled from bottles) got quite a lot of heavy ends in the reducer, and the filter magnet was "very furry".

My experiance is that we get a lot of oily deposits but nothing else. The vapourisers need cleaning every now and then but that is partly due to the way they are mounted.

We had lots of trouble with teh small Lovato vapouriser and had to change them very often. We now run the bigger Lovato vapouriser and they are not a problem. In fact some of them now have knocked up 2000+ hours of running. Other then cleaning them out and repairing worn pins and levers on some they have been great.

No problems on the single cylinder engine with the tank/bottle freezing but on twin cylinder engines running flat out I suspect it would become and issue.

Interesting range of views on this so I thought I'd chuck in my four penn'orth - I've worked for a generator company for the past fifteen years and we've made literally thousands of gas sets.

There's no set-up required on the Hondas when you use the basic kit. There's a doughnut adaptor that goes between the carb and air filter and it's jetted to suit the engine. You have a standard propane regulator and a Garretson "C" controller. That's the one with the sprung priming button which you press before starting to fill the intake with vapour since there's no depression to open the diaphragm.

You DON'T choke them!! That's why we like LPG for remote start because if you remote start a petrol, you have to fanny about with a choke solenoid. On LPG you simply use a Garretson "D" which doesn't have the priming facility but the fact that you're spinning over on a starter motor creates sufficent intake depression to open the diaphragm.

What you do need to do is choose a big enough bottle, according to the usage rate or you'll freeze up the gear. Hondas use 235g/hph or 310g/kWh (m).

The same setup goes on Briggs and Vanguards certainly up to 18hp though we have an exception in the Vanguard 575 which is a dedicated gas engine (with appropriate carb) not a converted petrol engine.

We've also done Kubotas, Listers, Fords and the biggest (which I designed myself) was a 100kVA based on an 8.1L GM V8 - lovely motor!! That was NG and unfortunately we couldn't get enough gas to it to fully load-test it so it only ever saw about 75% before shipping.